Abstract: Fan-delta distributary channel sand body is framework one of Xishanyao reservoir(Middle Jurassic)in Niujuanhu oilfield.The petrology of reservoir is characterized by low structural and compositional maturity.The lithology is feldspar-lithic sandstone and lithic sandstone.It has severe vertical heterogeneity, and can be classified into three members based on cyclic and vertical changes of petrophysical properties.Reservoir space is dominated by primary intergranular pore and secondary intergranular denudation pore, characterized by small pore and fine throat, small pore and tiny throat, fine skewness and poor sorting.Reservoi rquality is controlled by compaction, cementation and dissolution in A period of Late diagenetic period.There is better correlation between macro petrophysical parameters and micro structural parameters.Comprehensive evaluation indicated that two members in upper part are medium-bad reservoir, while lower member has no reservoir quality.Sensitivity analysis showed that the reservoir is strongly water-sensitive.

Key words: Santanghu basin, Middle Jurassic, Xishanyao formation, Reservoir characteristics, Pore structure, Diagenesis